Americum 241 has been used in smoke detectors.

CARLSBAD -- Thirteen employees (click here) of the Waste Isolation Pilot Plant were exposed to radiation, according to test results taken the day a radiation leak was detected at the nuclear waste repository.

The workers tested positive for americium-241, one of the radiation particles emitted from the transuranic waste deposited in the nation's only underground waste repository, located 26 miles east of Carlsbad, and were notified on Wednesday by Department of Energy and Nuclear Waste Partnership officials....

 










To the right is a dismantled ionization chamber and the Am 241 within it. Above to the left is microscopic examination of the Americum itself.

(Updated March 2013)
Smoke detectors/alarms (click here) are important safety devices, because of their obvious potential to save lives and property. There are two types of smoke detector commonly available in many countries.

One type uses the radiation from a small amount of radioactive material to detect the presence of smoke or heat sources. These 'ionisation chamber' smoke detectors are the most popular, because they are inexpensive and are sensitive to a wider range of fire conditions than the other type. They contain some americium.

The other type of detector does not contain radioactive material; it uses a photoelectric sensor to detect the change in light level caused by smoke. This type is more expensive to purchase and install, and is less effective in some circumstances....

The element Americum was artifically derived through the potential of plutonium-239.

Americium (click here) was discovered in 1944 by the American scientists Glenn T. Seaborg, Ralph A. James, Leon O. Morgan and Albert Ghiorso. They produced americium by bombarding plutonium-239, an isotope of plutonium, with high energy neutrons. This formed plutonium-240, which was itself bombarded with neutrons. The plutonium-240 changed into plutonium-241, which then decayed into americium-241 through beta decay. This work was carried out at the University of Chicago's Metallurgical Laboratory, now known as Argonne National Laboratory... 

Americum isotopes have different half-lives. Americum 241 has a half life of 423.7 years, so that is why it has to be contained. The use of this small amount of radioactive material in Fire Detectors is not medical use. There probably should be more containment of it's use and need. If we stop using radioactive material, where there are safer alternatives, in consumer products globally, it will stop so much need for containment facilities and the exposure of those that work with it.

The isotope has free electrons in it's outer shell. It is classified as a rare earth element.